The invention relates to watercraft sensors and to propeller safety devices and systems.
According to statistics kept by the U.S. Coast Guard, scores of people are killed or severely maimed each year from propeller injuries. Other mammals such as manatees are severely injured and disfigured and this problem threatens the tourism industry in areas such as Homosassa Springs State Park in Florida. The boating industry has struggled with this problem without much success for some time. The often proposed solution of using a mechanical propeller guard to physically block contact, while logical at first glance actually is very impractical, despite a number of attempts to implement this idea as described in U.S. Pat. Nos. 3,889,624; 4,411,631; 44,826,461; 4,078,516; 5,238,432; 4,957,4459; 5,009,620; 4,304,558; 5,759,075; 4,565,533; and 4,106,425. The guard would rob too much propulsion power and in some cases could increase the occurrence and severity of propeller injuries because the guard can act as a catch that prevents easy removal of a hand or foot from the propeller vicinity as commented on, for example by the Superior Court of Pennsylvania (Fitzpatric v. Madonna, 623 Aa.2d 322 1993), which stated that xe2x80x9cthe presence of a shroud over the propeller presents its own risks for swimmers. For example, a shroud creates a larger target area. In addition, the possibility exists that human limbs may become wedged between a shroud and the propeller, exposing a swimmer to even greater injury.xe2x80x9d
New propeller guard solutions have been proposed in view of the disadvantages of using a propeller guard. Another such proposal is a guard that moves away from the propeller at high speed as described in JP5,310,188. Another is a switch on a ladder that prevents a fossil fueled motor from engaging when a swimmer""s ladder is down, as described by Propeller Safety Technologies (Anderson Calif., www.propguardinc.com). A kill switch may prevent the problem of a passenger falling into the water during rapid boat movement. However, swimmers remain at risk of sudden contact with a boat at high speed. Others have mused over the possibility of sensing objects in the water (http://www.rbbi.com/invent/guard/propg/intro.htm) in a helpful effort to try and bring research groups working on animal and human detection in the water to think of this problem. However, there has been no solution that suitably accounts for the problems of motor inertia and the need for very rapid reaction times. Furthermore, most proposed solutions also do not address sufficiently the related problem of propeller contact with solid objects such as rocks while in operation. When the propeller is spinning rapidly during the contact, the propeller blades tend to quickly shear or grind down on the collided object, and can slice a human body many times in just one second.
In sum, the boating industry needs a low cost solution to propeller contact with solid objects. The issue of safety will become even more of a problem as the waterways become more and more crowded due to the obvious overpopulation and consequent egregious overuse of the limited resources of the planet. Accordingly, a system to prevent or alleviate this problem would help promote the boating industry make the waterways safer and allow even more commercially desirable overcrowding while minimizing damage from open propellers.
The invention provides a system for quickly stopping a propeller before the propeller can significantly damage a solid object that appears immediately upstream of the propeller. In embodiments of the invention an electronic sensor detects a solid object that enters a danger zone near the propeller and triggers a circuit that rapidly stops the propeller. In other embodiments a device records, monitors and reports in real time instances of sensing imminent contact of a propeller with a solid object.
Another embodiment provides a system to limit contact of a propeller having a diameter D with a solid object in a motor driven watercraft comprising at least one sensor that monitors a danger zone, the zone comprising a circular area of diameter D located distance D immediately ahead of the propeller perpendicular to the direction of motion and outputs a signal in response to intrusion of a solid object in the danger zone; and an activator electric control circuit that stops motor movement upon receipt of the signal.
Another embodiment provides a watercraft that contains a system for limiting propeller contact with a solid object in the water, comprising at least two monitor sensors attached to one or more control surfaces in the water and upstream of the propeller that output an electrical response upon detection of the solid object; and an electric control circuit that accepts the signal and stops motor movement upon the detection of the solid object.
Yet another embodiment provides an electrical control device for suddenly stopping a propeller in a motor driven watercraft, comprising a sensor that detects a solid object near the propeller and a control circuit that can stop or slow the propeller to less than 10 rpm within one second, wherein the sensor triggers the control circuit upon sensing the solid object.
Further embodiments will be appreciated from a reading of the specification.